Fix ubuntu 20.04 installation

[yurirocha15]

This should fix the recent issues (#31, #33) with the ubuntu 20.04 installation.

The issues were caused by updates on upstream dependencies:

• rapidjson failing to build tests -> fixed by not building them on the installation script (they are not needed here anyway)
• a pyopengl version released on May 2023, which is failing to install on python 2.7 -> fixed by pinning the package to the anterior version.